Such lighting devices are known, for example, from the document WO03/075249 A1. The base body, which is labeled with reference numeral 2 in FIGS. 1 through 9 of this document, is made of bent sheet metal. It is sealed with a light-conducting cover element 3 made of acrylic glass in particular. Using two-sided adhesive tape, the light-emitting diodes are glued to one of the two parallel sections of the U-shaped sheet metal body close to the transverse leg. The distribution of light over the total light-emitting surface of the U-shaped base body should occur due to reflection on the strips formed by the sheets. FIG. 8 shows a measure which should improve the illumination of the entire area. One angle is glued to the lower surface of the leg between the two sections of the U-shaped base body parallel to one another to permit reflection of the rays of light of the light-emitting diodes onto the entire area of the light-permeable light-emitting surface. Alternatively, the specific embodiments of the drawings in FIGS. 26 and 27 disclose a U-shaped sheet metal housing as the base body, which is open toward the wall and permits light to be emitted only toward the wall. Furthermore, a specific embodiment in which the visible front surface as well as the rear surface facing the wall is used as the light-emitting surface(s) is disclosed.
In all cases, the base body must have a substantial height in relation to its width in order to ensure that reflection of the beams of light on the walls of the U-shaped sheet metal housing will lead to complete illumination of the entire light-emitting surface.
The document US 2002/0159257 A1 describes a lighting device having a housing which includes a bottom and inside walls as well as a cover. A strip having electrical conductors, on which the light-emitting diodes are arranged, is applied to the external side wall of the housing. Here again, it is problematic to achieve homogeneous illumination of the visible surface. The document DE 299 12 986 U1 describes a symbolic luminous mark having a light-conducting body made of plastic, in particular in the form of a sheet, assembled with lights. The light-conducting sheet has a narrow channel in its lateral edge area in which light-emitting diodes are arranged. Alternatively, a narrow channel is applied in the middle of the plate, where light-emitting diodes sending light into the exterior regions of the plate are arranged back-to-back.
Accordingly, it would be desirable to create a lighting device which is easily manufactured and has excellent lighting properties, the base body of which may be designed to be very compact. In addition, it would be desirable is to create a method for manufacturing such a lighting device.